1. Field of the Invention
The present invention relates to a method and device for threading a web through a calender with a roll stack having several rolls which form nips between one another for treating a material web.
While the exemplary embodiment of the invention describes a paper web as an example of a material web, it is noted that the invention is analogously applicable to other material webs that have to be treated in a calender.
The design of the rolls themselves is not significant to the present invention. Both xe2x80x9chardxe2x80x9d as well as xe2x80x9csoftxe2x80x9d rolls can be used which alternate and these so-called xe2x80x9csoftxe2x80x9d nips or roll slits can therefore be formed. However, the calender can also have exclusively or predominantly hard rolls.
2. Discussion of Background Information
One type of calender is known from EP 0 232 689 A2.
Treating a paper web in a calender, known as glazing, takes place in many cases in off-line operation, i.e., the paper web is typically unwound by a reel spool, guided through the calender and then wound onto a new reel spool. Even if a so-called flying splice, i.e., a flying change between a used and new reel spool, is performed, from time to time it is necessary to guide the beginning of the paper web through the roll stack, for example, after the web has torn. This threading can take place manually which, as a rule, normally requires two members of the operating crew standing on either side of the roll stack. In this process, the paper web is folded together at its tip into an arrow shape and slid through the first nip. The operating crew member receives the paper web on the other side, guides it around reversing devices, as the case may be, such as guide rollers, and again inserts it into the next desired nip. This manual threading process is relatively time-consuming, laborintensive, and raises safety concerns. Even if the web of paper is moved in this case only at a relatively low speed of 10 to 20 m per minute, it can easily result in dangerous situations or even accidents.
In an effort to address these concerns, EP 0 232 689 A2 discloses the possibility of automating the insertion of the paper web. To do this, a web guidance device having a guide surface as well as a blower device is always arranged between two nips, i.e., always on one roll. The web hitting the guide surface is then slid along the guide surface in the desired direction with the aid of the blower device.
A calender structured in this way can be operated automatically in a certain respect. The danger that accidents to persons will occur during threading is also considerably less. However, the effort and thus the costs for the web guidance device are very high. Complicating this further is that the accessibility of the calender during operation is dramatically restricted. If a web tears, something which cannot reliably be avoided in practice, the web guidance device can cause dangerous paper jams which can cause resulting damage to rolls and other devices. Moreover, this design obstructs the view of the running paper web and makes changing the roll more difficult.
The present invention reduces the possibility of malfunction in operation by utilizing a threading device.
In particular, the present invention provides a calender of the type mentioned at the outset that also includes a movable web guidance device, which can be fixed in at least one insertion position, arranged on at least one side of a roll stack.
xe2x80x9cSidexe2x80x9d in this case does not refer to the face, but rather to the front or rear side of the roll stack on which the material web must be reversed in order to be guided into the next desired nip.
Thus, the advantages of a mechanized system are exploited without having to accept its disadvantages. The web guidance device is available for threading the beginning of the material web into the calender. In this threading process, however, it is possible to make do with a far lower constructive cost because the web guidance device can be moved from one insertion position to the next one. If the tip of the material web has been inserted into a nip, the web guidance device has performed its function at this point and is no longer required there. In the time that the paper web on the other side of the roll stack needs to be reversed and inserted into the next nip, the web guidance device can be shifted or moved to the next nip in order to receive the tip of the material web and again transport itself to the next desired nip. Based on this movement of the paper guidance device, it is clear that in operation most of the nips are free from the web guidance device so that it cannot cause malfunctions in operation. Nevertheless, threading or inserting the material web can be widely automated or at least mechanized so that the danger of accidents to the operating personnel remains low.
In one embodiment the web guidance device is initially fixed in a parked position where no nip is covered by the web guidance device. In operation, the material web can be observed just like in a calender which has been threaded by hand. That is, the device should not obstrict the view of the web travel through the nips. As a result, monitoring possibilities are improved quite significantly and the possibility of malfunctions is reduced still further.
The invention incorporates a traverser which is arranged advantageously on the side of the roll stack and the web insertion device is fastened to the traverser. Traversers are present in many calenders at any rate, and they are typically used for maintenance purposes, for example, to detach or fasten bearings of rolls being replaced. They can also be used to assist in manually operated threading of paper webs. Thus, using a conventional traverser makes a transport medium for the web guidance device available without greater additional expense.
In another embodiment, position switches are provided along the path of movement, each of which is assigned to an insertion position wherein these switches. are connected with a drive control. As a result of this design, the movement of the web guidance device can be controlled automatically or at least semi-automatically. In operation, the web guidance device is moved into the position where it receives the tip of the material web and/or can pass it on to the next desired nip. The position is determined, for example, by the position switch. If the web guidance device is moved into the next position, it also actuates the position switch there and thus reports the arrival to the drive control. On the other hand, provisions can be made in the drive control so that the web guidance device does not have to stop at every position, such as when some nips are supposed to be skipped when treating the paper web.
The web guidance device may advantageously have a guide surface arrangement. The tip of the paper web impacts the guide surface arrangement and is. guided in the desired direction thereby. The structural expense in this connection is relatively low.
Here, it is preferred for the guide surface arrangement in this connection to have a modifiable form. The guide surface arrangement can then also be used as xe2x80x9csoft.xe2x80x9d Thus, it is possible to guide the paper web either immediately into the next nip of the roll stack or to jump over several nips and guide the. paper web parallel to the roll stack if this is desired for the treatment of the paper web.
In this connection, it is particularly preferred for the guide surface arrangement to have an evenly formed surface running essentially parallel to the direction of movement of the traverser and a reversing surface that can be moved out of the evenly formed surface. As long as the reversing surface does not project beyond the evenly formed surface, the paper web will be guided essentially parallel to the roll stack, i.e., will be able to skip several nips. If, on the other hand, the reversing surface is moved out of the evenly formed surface, the paper web will be diverted in order to be inserted into the next nip.
Another embodiment is provided here in which the reversing surface is arranged on pivoted levers. The reversing surface will then be folded out, as it were.
In still another embodiment, provision is made for the reversing surface to be arranged on a sliding piece that can be displaced transverse to the direction of movement. Naturally, the two embodiments can also be combined, if this is useful for structural reasons or space considerations. While a change in the guide surface geometry is caused in the first case by a pivoting movement of the pivoted levers, the geometry is changed in the second case by a linear movement.
Another embodiment provides that the guide surface arrangement has at least. one tongue which can be displaced up to the roll stack. As a result, the paper web can be guided into the vicinity of the nips and, in many cases, even up to directly in front of the nip. In this connection, it is only required for the paper web to be supported until it comes to lie at an area of the lower roll of the nips in which further thrusting of the paper web is not obstructed or disturbed by a roll segment that is too steep.
According to another embodiment, which can be provided as an alternative to or in addition to the guide surface arrangement, the web guidance device has at least one gripper head which can be moved vertically away from the roll stack in a first motion segment, parallel to the roll stack in a second motion segment, and vertically towards the roll stack in a third motion segment. In this connection, these three movements need not absolutely occur completely separately from one another. They can also be combined in such a way that the entire movement of the gripper head corresponds approximately to a semicircle. The gripper head can grasp the paper web which is being advanced through the nip, pull it out of the roll stack, pull it to the next desired nip and re-thread it there. Compulsory guidance occurs as a result, which is particularly advantageous with thinner paper, because its stiffness is not sufficient in some cases to push it through the individual nips.
According to still another embodiment, the gripper head has a suction and/or a blower device. In this design, the gripper head does not have to be fed through a nip in order to thread the paper web. On the contrary, it can remain in front of the nip in order to suction the paper web there. If the gripper head holds the paper web ready in front of the next nip, it can release it and blow it through the nip with the aid of a blast of air.
The gripper head can also be rotated 180xc2x0 around an axis running parallel to the axes of the rolls. This takes into account the fact that the beginning of the paper. web must change direction in the same way in order to be inserted into the next desired nip.
In this connection, it is especially preferred for the gripper head to grip the material web laterally. Then the twisting of the gripper head does not produce any deflection of the paper web at its tip. On the contrary, the paper web is guided through the nips relatively smoothly.
The threading device can also be used on roll stacks which are inclined. Precisely in the case of stacks of rolls that are diagonal, the problem of threading the paper web is especially aggravating. While it is still possible in many cases to reach the paper web from below without there being great danger to the operating personnel, it is no longer possible to do so as easily from above. The web guidance device facilitates this process greatly particularly at the traverser.
According to one aspect of the invention, there is provided a web guidance device for a calender which includes a roll stack having several rolls which form a plurality of nips, the device including a movable web guidance device which is fixable in at least one insertion position and arranged on at least one side of the roll stack, wherein the web guidance device guides a beginning of the web through the roll stack. The calender may be a material web treating calender. The web guidance device may be fixable in a parked position in which no nip is covered by the web guidance device. The device may further include a traverser coupled to the moveable web guidance device. The web guidance device may be fastened to the traverser. The device may further include position switches for detecting the position of the web guidance device, the position switches being connected with a drive control. The web guidance device may further include a guide surface arrangement. The guide surface arrangement may include moveable guide surfaces for guiding the web. The at least one moveable guide surface may be an evenly formed surface which runs essentially parallel to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack. The guide surface arrangement may further include a reversing surface extending from the evenly formed surface. The reversing surface may be moveable to a position parallel to the evenly formed surface. The reversing surface may be arranged on pivoted levers. The reversing surface may be arranged on a sliding piece which is moveable in a direction substantially perpendicular to the stack plane. The guide surface arrangement may further include at least one tongue for engaging the web beginning, the at least one tongue being moveable in a direction substantially perpendicular to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack.
The web guidance device may further include at least one moveable gripper head for engaging the web beginning. The gripper head may be moveable along a arcuate path relative to the stack plane. The gripper head may be moveable in a direction substantially perpendicular to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack. The gripper head may be moveable in a direction substantially parallel to the stack plane. The gripper head may include one of a suction and a blower device for engaging the web beginning. The gripper head may be rotatable for at least 180xc2x0 around an axis running parallel to an axis of at least one roll in the roll stack. The gripper head may include jaws which are oriented substantially parallel to an axis of at least one roll in the roll stack.
The device may provide that the roll stack is inclined at an angle. The angle may be in the range of approximately greater than 0 degrees and less than 90 degrees.
The invention also provides for a device for threading a material web through a calender which has a roll stack having at least a first nip and a second nip, the device including a platform which is moveable relative to the roll stack and arranged on one side of the roll stack, and a web guidance device coupled to the platform, wherein the web guidance device is adapted to redirect the direction of the material web after the web passes through the first nip. The platform may include a traverser for carrying a operating personnel. The traverser is moveable in a direction parallel to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack. The web guidance device may include at least one pivoting lever having a guide surface for engaging the web. The web guidance device may include two pivoting levers each having a guide surface for engaging the web. The guide surface of each lever is curved whereby the web is guided to the second nip after reversing direction. The web guidance device may further include a linear guide coupled to the pivoting levers, the linear guide being oriented parallel to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack. The web guidance device may further include fluid activated cylinders for moving the pivoting levers. The web guidance device may also include at least one sliding mechanism having a guide surface for engaging the web. The web guidance device may provide that at least two sliding mechanisms each having a guide surface for engaging the web. The guide surface of each sliding mechanism may be curved whereby the web is guided to the second nip after reversing direction. The web guidance device may further include a linear guide coupled to the pivoting levers, the linear guide being oriented parallel to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack. The at least one sliding mechanism may further include a tongue disposed at one end of the at least one sliding mechanism for engaging the web, the tongue being retractable into the sliding mechanism. The web guidance device may include at least one guiding mechanism having an end for engaging the web. The guiding mechanism may include a connecting rod which is moveable in a direction substantially perpendicular to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack. The connecting rod may include a gripper head for engaging a beginning end of the web. The gripper head may include a pair of rotating jaws for reversing the direction of the web. The gripper head may have one of a suction and a blower device for engaging the web beginning. The platform may travel along a path which is parallel to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack. The path may further include position switches for detecting the position of one of the platform and the web guidance device. The position switches may be connected to a drive control device.
The invention also provides for a method of threading a material web through a calender which has a roll stack having at least a first nip and a second nip, the method includes feeding a web beginning through a first nip from one side of the roll stack, engaging the web beginning on the other side of the roll stack with a web guidance device, and guiding the web beginning to a second nip with the web guidance device. The web guidance device may be coupled to a moving platform. The guiding may further include reversing the direction of the web beginning. The engaging may further include gripping the web beginning with a gripper head disposed on the end of the web guidance device. The gripping may further include vacuum retaining the web beginning. The gripping may further include rotating the web beginning approximately 180 degrees. The engaging may further include pivoting at least one lever having a web guiding surface. The engaging may further include pivoting two levers each having a web guiding surface. The engaging may also include moving at least one sliding mechanism substantially perpendicular to a stack plane, the stack plane running through a center axis of at least two rolls in the roll stack.
The method may further include moving the web guidance device from a parked position to a first position for initially engaging the web beginning. The method may further include detecting the position of the web guidance device with position sensors disposed along a web guidance device travel path. The method may also provide that the first and second nips are separated in the roll stack by at least one intermediate nip. That the first and second nips are separated in the roll stack by at least two intermediate nips. That the first and second nips are separated in the roll stack by at least two intermediate nips.
According to still another aspect of the invention, there is provided a device for threading a material web through a calender which has a roll stack having at least a first nip and a second nip, the device including a platform which is moveable along a travel path, the travel path being parallel to a stack plane whereby the stack plane runs through a center axis of at least two rolls in the roll stack, a web guidance device coupled to the platform, the platform being arranged on one side of the roll stack, the path including position sensors for detecting the position of one of the platform and the web guidance device, and a mechanism disposed on the web guidance device for changing a first direction of the web exiting the first nip to a second direction entering the second nip.
The invention also contemplates a method of threading a material web through a calender which has a roll stack having at least a first nip and a second nip, the method including moving a web guidance device from a parked position to a first position adjacent the first nip, detecting the first position with a position sensor, feeding a web beginning through a first nip from one side of the roll stack, engaging the web beginning on the other side of the roll stack with the web guidance device, changing the direction of the web beginning with the guidance device, and moving the web guidance device back to a parked position.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.